1. Field of the Invention
The invention relates to a mixing board for sound signals, in particular a mixing board for a disc jockey (DJ) which includes the functions of pre-listening to the sources, changing the timbre, and cross-fading/mixing two sources to one output.
2. Description of the Related Art
Normally, DJ mixing boards process so-called low-frequency analogue signals (commonly called line or cinch signal) or record player signals having standardized voltages.
These signals must be electronically amplified in order to be suitable for processing in a DJ mixing board since signal processing entails signal losses (voltage losses). Electronic amplification always requires a power supply to be available.
As an alternative, digital signal processing can be performed, but this type of signal processing also requires a power supply (GB 2431285 A).
To be able to change the timbre of a sound signal in a DJ mixing board, passive sound filters are normally used. Signal processing by means of passive sound filters, however, entails signal losses (voltage losses). To compensate for said losses, the signal must be amplified with the aid of a power supply either ahead of or behind the filter.
To conveniently cross-fade from one signal source to a second signal source, a cross-fader is used in DJ mixing boards. The circuit connects one signal source with the ground by means of a slide potentiometer (the cross-fader) so that the other source will be heard at the output.
In the middle position, both signal sources can be heard. The analogue circuit of the cross-fader usually entails a voltage division due to two follow-on resistances; in this case, the voltage is divided in half, which must then be compensated for by means of an amplifier including a power supply (WO 01/11809 A1).
The pre-listening function in a DJ mixing board is usually accomplished by means of active electronic circuits. The input signal is divided and amplified separately for the headphone socket of the mixing board.
The drawbacks of such conventional DJ mixing boards are the own power supply required, the weight and the larger size, which limit mobility and flexibility and ultimately also cause higher costs.